The National Centers for Environmental Prediction (NCEP) is a component of the Climate Prediction Center (CPC). A prototype, real-time, hourly, multi-sensor National Preciptation Analysis (NPA) has been developed at NCEP in cooperation with the Office of Hydrology (OH). This analysis merges two data sources that are currently being collected in real-time by OH and NCEP. Hourly digital precipitation (HDP) radar estimates are created by the WSR-88D Radar Product Generator on a 131 X 131 4-km grid centered over each radar site. Data analysis routines, including a bias correction of the radar estimates using rain gage data, have been adapted by NCEP on a national 4-km grid from algorithms developed by OH and executed regionally at NWS River Forecast Centers (RFC). This data set contains the NCEP 4 KM GRIB Data including multi-sensor analysis (gage and unbiased radar), gage-only analysis, radar estimate, and radar estimate after bias removal. Depending on the time period selected, all four types may or may not be available. This data set is provided as is and was not quality controlled by UCAR/JOSS.